I live in Indiana but I think I was very briefly getting WSOR 90.9!!

I live in northern Indiana and this is the farthest I've heard an FM Station. The farthest AM was KOA 850 in Denver.

Unfortunately I wasn't receiving it long enough to hear the Station ID but my radio has Program Service Data and it said WSOR on the display.

E-skip is alive and well, my friend. There were paths from MI-FL on FM, so your path definitely matches. One reason why I love summer, had a big opening here in WA a couple nights ago with 10 new stations logged from SD to NM/CO, and some frequencies had 2-3 stations swapping.

I get WTAM every night.

AM prop and FM prop are two different things. AM propagation is skywave, the F-layer in the ionosphere. Once the sun goes down, East Coast and Midwest stations are usually heard every night in Indiana. And it's reliable 365 days a year. However, there are times where the conditions can be stronger or auroral depending on solar activity. Low solar activity is REALLY good for mediumwave/AM...out here I know conditions are really good when WBBM is listenable under Reno on 780, or when I hear weak ESPN on 1530 under KFBK (WCKY Cincinnati, of course). Auroral activity can be amazing on the east coast - I know many DXers in the northeastern United States that can often hear Mexico, Venezuela & Colombia on AM when the Northern Lights are out. Of course there's a LOT of Cubans in the way...
The E-layer in the ionosphere causes the odd summertime phenomena that is sporadic-E skip. This is all high HF and VHF - 50mhz/6-meter ham band is one of the best beacons for activity. Back in the good ole days we had TV channels 2-6, and the interference and rolling bars were a sign of skip. Sometimes the 'clouds' favor the south, other times the west, or another direction.